Field of the Invention
The present invention relates to an ophthalmologic apparatus and a method thereof.
Description of the Related Art
In the related art, in an ophthalmologic photographing apparatus represented as a non-mydriatic fundus camera, photographing is performed such that an operator performs precise position alignment, between an apparatus and an eye to be inspected in horizontal and vertical directions and a working distance (back and forth) direction while viewing an observation image captured by an image pickup element. This precise position alignment in horizontal and vertical directions and the working distance (back and forth) direction is performed such that an index projected onto an anterior ocular segment of the eye to be inspected is captured by the image pickup element, and the alignment is performed with reference to the captured index image.
Here, focusing on position alignment, in the working distance direction, JP S62-34530 A discloses a fact that, when the working distance between the apparatus and the eye to be inspected is appropriately positioned, a contrast of the index image is maximized. Meanwhile, when the working distance between the apparatus and the eye to be inspected is not appropriately positioned, a contrast of the index image decreases. An operator completes the position alignment in the working distance direction by manipulating the apparatus back and forth such that the contrast of the index image is maximized.
Recently, there has proposed an ophthalmologic photographing apparatus in which a position alignment state between the apparatus and the eye to be inspected in horizontal and vertical directions and a working distance (back and forth) direction is detected in an apparatus side as disclosed in JP 3569026 B1.
As a first problem, in the ophthalmologic photographing apparatus disclosed in JP 3569026 B1, when the position alignment state between the apparatus and the eye to be inspected in horizontal and vertical directions and a working distance (back and forth) direction is not accurately detected in the apparatus side, a flare from a cornea or a lens occasionally enters a photographing image. In addition, as a second problem, since a time for which the eye to be inspected can maintain a fixation state is significantly short, it is necessary to detect the position alignment state between the apparatus and the eye to be inspected in horizontal and vertical directions and working distance (back and forth) direction at a high speed.
In order to address the two problems described above, in the apparatus side, it is necessary to detect the position alignment state between the apparatus and the eye to be inspected in horizontal and vertical directions and a working distance direction with high precision at a high speed.